My house it the PERFECT example of black dog hair. When I empty the vacuum canister there is so much black hair, it's like I am throwing out another dog!!!!
My husband swears I'm trying to collect a complete set of dogs of varying sizes and colors. We just need a yellow dog, a gray dog and a toy dog to complete our set! We've already got a an extra large brown dog, a small white dog, a large red dog, and a medium black dog. When you whir the fur together in the vacuum canister, it looks gray.
When I volunteered at an animal control shelter, the only time I saw black dogs in particular being passed over was if we had a large number of them, and since black labs are very popular, there were many occasions when we had an overabundance.
Small dogs of any color (and of ANY tempermant) went long before large dogs of any color.
Large dogs and dogs of certain breeds were a difficult sell. You can't give a Chow away. (Oh, well apparently you can sometimes, since we have one.)
Dogs in the 5-10 month range are also difficult to place. People are generally either looking for a little puppy or an adult dog. The dogs in that age range are neither.
Large litters were bad too simply because you had a large number of a single breed/size when the chances of 10 people wanting that particular breed/size in a short period of time are slim. A few would find homes and the others would languish, growing up in the shelter (like our dog #4 who grew up in the shelter without ever having anyone interested in her -- and she's a GEM!)
It sounds as if your Katie had several things against her -- black dog, middling age (neither puppy nor adult), overabundant breed, and large breed. Very sad. Very frustrating. Glad she "won the lottery" and found you!